Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0278883 (metastatic melanoma)
 6,224 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An inverted pH gradient across the cell membranes is a typical feature of malignant cancer cells that are characterized by extracellular acidosis and cytosol alkalization. These dysregulations are able to create a unique milieu that favors tumor progression, metastasis and chemo/immune-resistance traits of solid tumors. A key event mediating tumor cell pH alterations is an aberrant activation of ion channels and proton pumps such as (H+)-vacuolar-ATPase (V-ATPase). TM9SF4 is a poorly characterized transmembrane protein that we have recently shown to be related to cannibal behavior of metastatic melanoma cells. Here, we demonstrate that TM9SF4 represents a novel V-ATPase-associated protein involved in V-ATPase activation. We have observed in HCT116 and SW480 colon cancer cell lines that TM9SF4 interacts with the ATP6V1H subunit of the V-ATPase V1 sector. Suppression of TM9SF4 with small interfering RNAs strongly reduces assembly of V-ATPase V0/V1 sectors, thus reversing tumor pH gradient with a decrease of cytosolic pH, alkalization of intracellular vesicles and a reduction of extracellular acidity. Such effects are associated with a significant inhibition of the invasive behavior of colon cancer cells and with an increased sensitivity to the cytotoxic effects of 5-fluorouracil. Our study shows for the first time the important role of TM9SF4 in the aberrant constitutive activation of the V-ATPase, and the development of a malignant phenotype, supporting the potential use of TM9SF4 as a target for future anticancer therapies.
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PMID:TM9SF4 is a novel V-ATPase-interacting protein that modulates tumor pH alterations associated with drug resistance and invasiveness of colon cancer cells. 2565 76

Cancer cell cannibalism is currently defined as a phenomenon in which an ensemble of a larger cell containing a smaller one, often in a big cytoplasmic vacuole, is detected in either cultured tumor cells or a tumor sample. After almost one century of considering this phenomenon as a sort of neglected curiosity, some recent studies have first proposed tumor cell cannibalism as a sort of "aberrant phagocytosis", making malignant cells very similar to professional phagocytes. Later, further research has shown that, differently to macrophages, exclusively ingesting exogenous material, apoptotic bodies, or cell debris, tumor cells are able to engulf other cells, including lymphocytes and erythrocytes, either dead or alive, with the main purpose to feed on them. This phenomenon has been associated to the malignancy of tumors, mostly exclusive of metastatic cells, and often associated to poor prognosis. The cannibalistic behavior increased depending on the microenvironmental condition of tumor cells, such as low nutrient supply or low pH, suggesting its key survival option for malignant cancers. However, the evidence that malignant cells may cannibalize tumor-infiltrating lymphocytes that act as their killers, suggests that tumor cell cannibalism could be a very direct and efficient way to neutralize immune response, as well. Tumor cell cannibalism may represent a sign of regression to a simpler, ancestral or primeval life style, similar to that of unicellular microorganisms, such as amoebas, where the goal is to survive and propagate in an overcrowded and very hostile microenvironment. In fact, we discovered that metastatic melanoma cells share with amoebas a transmembrane protein TM9SF4, indeed related to the cannibal behavior of these cells. This review attempts to provide a comprehensive description of the current knowledge about the role of TM9SF4 in cancer, highlighting its role as a key player in the cannibal behavior of malignant cancer cells. Moreover, we discuss differences and similarities between tumor cannibalism, entosis, phagocytosis and emperipolesis.
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PMID:Cancer Cell Cannibalism: A Primeval Option to Survive. 2651 9